Photoelectric plethysmography was employed to record amplitude changes in pulsatile blood flow from each of the supraorbital fields during carotid compression in 75 patients schedules for carotid angiograph. A testing method was developed on the basis of these data to detect carotid obstructive patients. The study result showed that with the developed method, 67 percent of the patients with radiologically significant carotid obstruction and 91 percent without it were correctly identified. It suggests that the developed method provides a rapid non-invasive test for unilateral carotid stenosis or occlusion. A report of this study was published in the March issue of the IEEE Transactions on Biomedical Engineering, 1980.